Didn't Sony have a patent to embed information on the Blu-ray, potentially to prevent resale?It was speculation based on "If Microsoft is doing it, then Sony must be doing too." That's where the "SonyToo" meme came from back on gaf. There has never really been any concrete information indicating that they were doing it too and only backed off because of the backlash Microsoft was receiving. Or that they changed their E3 conference to reflect that.
Edit: yes: https://www.giantbomb.com/forums/playstation-4-8451/sony-s-ps4-drm-plans-detailed-in-january-2013-pate-1439755/
Literally to control used game sales, says that article.